In marsh and swamp seismic prospecting, geophone cable spreads are used, each including a through cable having electrical junctions at spaced intervals from which leader cables are dropped. The through cable is layed along the ground. At the end of each leader cable is a geophone case which is implanted with a special tool into the mud for detecting returned seismic waves. In each junction box the conductors of the through cable and of the leader cable are suitably electrically joined together.
There are two commercially known T's which are presently being widely used. One is a completely molded T around the cables' junction providing no access to the electric wires; the other is a fastened T formed from two half-T's which are clamped together around the junction, and then the inside of the T is filled with a suitable potting compound. Both known T's provide a waterproof junction, but the molded T is impossible to repair in the field because the seismic crew has no injection molding equipment, while the fastened T requires considerable skill and time first to dismantle and remove the potting compound and then to re-assemble and to reshoot the compound into the T. To carry out the repair job, there is a need for special purpose tools and sealing compounds which are not generally available in remote areas, as in jungles or swamps.
For the following reasons it may be necessary to inspect or repair a wire junction within a T: cables and T's are frequently damaged by physical objects and their outer jackets and housings are eaten up by rodents; leader cables are dropped typically from the side of a pontoon and then to retrieve them a crewman is supposed to pull on the leader cable but instead he will frequently grab each T and pull on the T to retrieve the leader cable and the geophone case at the end thereof. Since the known T's do not include anchoring means, a strong pull on the T itself will break the electric connections inside the T, or break its waterproof seal, or even completely sever the T from its leader cable. Thus, a very costly entire geophone cable spread may have to be discarded for failure of a single T, or if a field repair job is attempted, very expensive field crew time is lost in repairing the fastened T in accordance with prior practice. The molded T is not field repairable, as previously mentioned.
It is a main object of the present invention to overcome the above mentioned drawbacks of the known T's and to provide a coupler serving as a waterproof junction box which allows access to the junction without requiring molding facilities, special purpose tools for assembly and disassembly, sealing compounds and potting guns. It is another object to provide an internal anchor for securing the electric conductors inside the junction box so that a pull on the box itself will not ordinarily rupture the junction therein or damage the waterproof seal.